The Basic Research Of New Media Of Carbon Nanotubes As Bionic Channel For Seawater Desalination

Forward osmosis （FO） as a potential technology for water purification anddesalination, causes the concern of people. It is very crucial to select the appropriatemembrane, which restricts the technology out of the laboratory and large-scaleapplication. Carbon nanotubes build FO membrane as simplified theoretical model touse the desalination field for solving the concentration polarization and low water fluxin process of FO. In this study, the density distribution, diffusion coefficient, waterflux and salt rejection of water molecules and ions through the membranesincorporating the carbon nanotubes （CNTs） with different sizes, in forward osmosis（FO） process are studied by means of the molecular dynamic simulation.First, the neutral “armchair”（R,R） carbon nanotubes, R=6^-11, build the forwardmembrane with the different concentrations of sodium chloride solution on the twosides of the membrane. The simulation results show that the diffusion rate of watermolecules in the carbon nanotubes is very fast. Only water molecules can pass forCNT（6,6）、CNT（7,7）、CNT（8,8）、CNT（9,9）, and the salt rejection are all100%. themembrane incorporating CNT（8,8） can achieve not only the optimum salt rejectionproperty but also the largest water flux When the nanotube diameter increases toCNT（10,10）、CNT（11,11）, sodium ions pass into the draw solution from the feedsolution, thereby reducing the salt rejection rate.Spurred by the traditional membrane science in which the charged membrane canimprove separating efficiency, this work tried to configure forward osmosismembrane by the charged “armchair type” carbon nanotube （R, R）,R=(8^-10). In thesimulation, the draw solution is sodium chloride solution with0.5mol·L^-1, the drawsolution is magnesium chloride solution with1mol·L^-1, and density distribution,diffusion coefficient and water flux are studied in the carbon nanotubes modified bythe different charges. The results show that, for the CNT（8,8）、CNT（9,9）、CNT（10,10） with the increase of the charge in the entrance of the nanotube, the radial and axialdensity distribution of water molecules inside the carbon nanotube appearhomogeneous, the diffusion coefficient also increases. CNT（8,8）、 CNT（9,9）、CNT（10,10）modified by-0.3e, the distribution of water molecules in the nanotubeshows the most homogeneous state; Where the charge for the water moleculesthrough the CNT（8,8） is the most significant,-0.3e modified carbon nanotubes, waterflux achieve maximum; For salt ions through CNT（10,10）, rate of salt rejection occursthe minimum value, when carbon nanotubes modified by-0.3e.In a word, as a kind of foundational and explored study, this work can offertheoretic reference and technical support for research of limited liquids in carbonnanotubes by the means of studying microscopic property and conduction for limitedwater molecules and ions.